Sheet feeding mechanism



United States Patent Inventor Harry Pilitz Glendale, New York Appl. No. 705,531

Filed Feb. 14, 1968 Patented Nov. 24, 1970 Assignee Crown Cork & Seal Company, Inc.

Philadelphia, Pennsylvania a corporation of New York. by mesne assignment SHEET FEEDING MECHANISM 6 Claims, 5 Drawing Figs.

US. Cl .l 271/54, 271/84 lnt.Cl. B65h 5/04, B65h 29/46 Field ofSearch 271/54, 60,

84; 100/Burr [56] References Cited UNITED STATES PATENTS 1,888,659 11/1932 Eckhard 271/54 2,672,835 3/1954 Paul 271/54X 2,872,189 2/1959 Robinson 271/54 Primary Examiner-Edward A. Sroka Attorney- Sawyer and Kennedy ABSTRACT: A mechanism for use in metal decorating presses to push the sheets to be fed into the machine up to the front stops and grippers of a printing couple. A plurality of pneumatic cylinders exerting pressure on the back edge of the sheet. The amount of force exerted by the cylinders is adjustable so that proper feeding of the sheets takes place regardless ofthe weight or thickness ofthe sheet.

Pa tentecl Nov. 24, 1970 3,542,359

Sheet 1 of 3 I NVENTOR Patented 'Nav. 24, 1970 3,542,359

FIG. 2

I N VENTOR.

Patented Nov. 24, 1970 I 3,542,359

Sheet 3 of3 INVENTOR.

SHEET FEEDING MECHANISM A limitation on the speed of operation of such equipmentv has been the tendency ofthe sheet to bounce, buckle or fail to engage both front stops properly at the time the grippers close, so that the printing is out of registry. It has been observed that the springs used for urging the pushers against the sheet may,

be changed with advantage when printing sheets of different thickness and stiffness, a change to the most appropriate spring for a given type of work being definitely advantageous in reducing the defects indicated above. As speed is increased, however, these defects reappear, even despite the use of the optimum spring and, prior to the present invention, it has not been possible to locate the cause of such defects or to correct them.

It is the general object of the invention to provide an improved pusher mechanism permitting material increase in operating speed without faulty operation in the above indicated particulars.

Another object of the invention is to provide a pusher mechanism in which the urging force exerted can be measured while the equipment is running at operating speed and also providing for the maintenance of this pusher force at a substantially constant value.

In the preferred embodiment of the invention, there is substituted for the springpressed pusher mechanism of previous equipment, a pusher mechanism utilizing a pneumatic cylinder together with adjustable automatic pressure control. This equipment permits the setting of pressure to proper value as previously determined for the type of sheet involved and speed of operation and, if desired, the increasing and decreasing of this pressure during the operation of the equipment so as to determine the point at which buckling commences as the pressure is increased and also the point at which misalignment of the sheet begins to appear as the pressure is decreased. The operating pressure may then be set between these values. While a close adjustment is provided, it is found that sufficient range exists to permit a rapid and certain determination ofthe proper operating point.

With the above mentioned objects as well as others which will appear in the following description in mind, the preferred embodiment of the invention will now be described with reference to the accompanying drawings and the features forming the invention will then be pointed out in the appended claims.

DESCRIPTION or THE DRAWINGS In the drawings: FIG. 1 is a floated isometric showing relevant parts of a sheet feeding mechanism embodying the pusher mechanism of' DESCRIPTION OF THE-PREFERRED EMBODIMENT OF THIS INVENTION A mechanism according to the invention may actually be constructed by substituting for the pusher mechanism of an existing machine the improved mechanism of the present invention, together with the required pneumaticconnections and equipment. Such substitution permits a comparison of performance with all other factors unchanged and this comparison has demonstrated reliable operation at very materially increased speeds. For simplicity, the invention will be described with reference to such. a machine (substantially as shown in the above mentioned patents), describing the known elements of such machines herein only to the extent necessary for an understanding of the present invention.

In FIG. 1 there is shown a pair ofpusher mechanisms 1 fixed to slide bars 2 which slide in on tracks or rails 3 by means of brackets 4. A number of tapped holes 5 in the bars 2 permit the fastening of the pusher mechanisms 1 at any desired point along the bars 2 by means of screws 6. A cross frame member 7 of the machine is utilized to support air tubing 8 which connects by means of flexible hoses 9 to the pusher mechanisms. Bars 10 also supported on the crossmember 7 support the hoses 9 and carry posts 11 around which the hoses pass to prevent their dropping into a position where they interfere with other elements of the mechanism. The action of the parts other than the pusher mechanisms themselves is as described in the above-mentioned patents and will be reviewed here only briefly and to the extent necessary for an understanding of the present invention.

- The bars 2 slide back and forth on their rails 3 between an extreme position of approach to the printing machine (the position of FIG. 2) and a remote position (not shown) where they pick up the sheet. The pusher frame element 12 is pivotally secured to the bracket 4 by means of a pin or stub shaft 13, so as to move with the bracket along track 3 while permitting a pivotal movement around the axis of the shaft 13. The opposite face of the frame 12 (FIG. 3) carries a roller 14 which runs in a track 15 for holding the pusher frame in the horizontal position of the FIGS. during the forward movement of the pusher frame. When pusher element 12 on bracket 4 approaches the extreme position mention-d above, a slider 37, which is attached to the pusher moving sprocket chain 38, moves downward in a vertically arranged crosshead 36, which is part of pusher element 12, while traveling around the arc of the sprocket wheel. Track 15 in which roller 14 is guided, is pivotally mounted on a stud 41 by a bracket 42 and is cyclicly lowered and raised by a track operating cam (not shown in the drawing). By this operation, pusher element 12 swings about stub shaft 13 down in the extreme forward position so that pusher 16 sinks below the plane of feed and is raised again at the remote position for engaging the rear end of a new sheet to be forwarded into the printing machine. This mechanism corresponds to the device which has been described in detail in the Eckhard U.S. Pat. No. 1,888,659, mentioned above.

The pusher arm 16 which constitutes the pusher element proper has a fork 17 formed on its lower end, which is pivotally secured by pin 18 to the frame structure of the pusher. Intermediate its length, the pusher arm 16 carries a pin 19 by means of which it is pivotally attached to a pair of links 20 which, in turn, are pivotally attached to a pin 21 to the end 22 of a piston 23 which reciprocates in cylinder sleeve 24 fitted into a bore 25 formed in the frame member 12. Bores 26 and 27 lead from the end of the cylinder space to a fitting 28 to which air hose 9 is attached. The air hose 9 (FIG. 1) lead to a pair of pressure gauges 30 and adjustable pressure reducing valves 31 which, in turn, connect through piping 32 with an air filter 33 supplied through connection 34 with air from any available source, such as a shop airline, or by means of an air compressor unit. The pressure reducer valves 31 are of any suitable type which will maintain constant outlet pressure, any of various diaphragm operated valves available on the market having the required sensitivity of response and accuracy of control.

As shown in FIG. 2 a sheet S is fed by the pusher arm 16 over the machine cross frame element 7 and over a support plate 35 carried thereby to the nip ofa printing couple 8,1 (ordinarily the blanket cylinder and impression cylinder of an offset printing unit) so as to come up against stops and under grippers (not shown) carried by the impression cylinder. The slide bars 2 carry vertical crossheads 36 cooperating with slides 37 pivotally secured to sprocket chains 38 so that the continuous movement of the sprocket chains first advances a pusher to the limit of its feeding movement as shown in FIG. 2 and then returns it to its limit of movement in the other direction where it picks up another sheet, this cycle being repeated for feeding the sheets in the usual way.

In the ordinary operation of the machine, the parts are timed so that the sheet will be accepted by the gripper of the impression cylinder when the pusher is in the dotted line position of FIG. 2, corresponding to the point where slide 37 ceases to move horizontally and commences to follow around the arc of the chain as it passes around its sprocket wheel. Up

to this dotted line position, the pusher is moving at substantially the linear speed of the printing machine, or slightly faster (e.g., one-half percent) and the forward edge of the sheet propelled by it, if moving at the same speed as the pusher mechanism at the time it engages the printing machine front stops will be traveling at a somewhat greater speed (due to the component of the peripheral speed of the stops in the direction of feed of the sheet being less than the full peripheral speed of the stops). Unless the pusher mechanism will yield in a proper manner, there is, therefore, danger of buckling as mentioned above. As slide 37 travels around the arc of the sprocket wheel, the speed of the pushers is harmonically reduced to zero while they sink downwardly as it has been described above, so that the rear edge of the sheet leaves the pushers without any mechanical interference.

The sheets as picked up by the pushers are ordinarily traveling at a somewhat slower speed (again, by about one-half per cent) than the pushers, so that the sheets are slightly accelerated.

The length of stroke of the air cylinder is selected, so as to accommodate for an extreme condition which actually does not occur in practice, namely the difference between the travel of a sheet after engagement by the pusher, when traveling at the speed of the pusher frame 12, as compared with the travel of the sheet if-traveling at the speed when engaged by the pushers. This distance is ofthe order ofone-half the stroke of the piston, which relationship insures that even should the air pressure fail or be set by accident at far too low a level, the pushers will still yield by only a fraction of the'total movement permitted by the air cylinder and link connections.

As noted above, sliding block 37 moves at uniform speed in the feeding direction throughout its movement along a straight course of the sprocket chain, and decelerates harmonically as the pin pivotally connecting it to the sprocket chain travels around the sprocket wheel. Brackets 4 being fixed to slide bars 2, have positions varying in accordance with the length of the sheet, it will be apparent'that if the parts are dimensioned so that a sheet of the shortest length provided for (e.g., 18 inches) is accepted by the grippers of the printing couple before the deceleration of pusher mechanism frame 12 commences, the acceptance. of longer sheets (e.g., 48 inches) will occur at an earlier point before this deceleration, so that there will be a substantial amount of pusher travel at full speed, following the taking of the leading edge of the sheet by the printing couple grippers, requiring for the longer sheets a yielding movement during this interval which is a substantial fraction (as, for example, one third) of the entire movement of pusher arm 16 which is permitted by the stroke of the air cylinder. With spring constructions as heretofore used, this entails a very substantial spring compression with increase of pressure in proportion to the spring rate. Since this building up of pressure occurs after the sheet has firmly encountered the front stops, it will be apparent that it can serve no useful purpose and only cause trouble. An attempt to eliminate this difficulty by softening the spring will result in its failure to engage the sheet with both front stops if the sheet should be presented in a siightly skewed position.

1th the mechanism of the invention, however, the air pressure is set at a value such as to insure the printing of a skewed sheet and, even if there should be a substantial backward yielding movement ofthe pusher arms thereafter, practically no additional pressure will be built up. The air cylinder piston is preferably fitted with a sufficient clearance so as to bleed a steady and substantially constant quantity of air. permitting restoration of desired pressure by lead leakage around the piston, if the pressure is even slightly disturbed. in addition, the automatic pressure control valve will adjust the supply of air to the cylinder so as to restore the set pressure practically instantaneously in response to any disturbance.

While the invention has been described and illustrated with respect to a certain preferred embodiment which gives satisfactory results, it will be understood by those skilled in the art after understanding the principle of the invention, that various other changes and modifications may be made without departing from the spirit of the invention.

1 claim:

1. In a sheet feeding mechanism having reciprocating elements operating in timed relation to a printing machine for reciprocating elastically yielding pusher mechanisms engaging the rear end of successive sheets and feed the same to said printing machine, the improvement of the combination with said reciprocatingelements of said pusher mechanisms, each of which comprises a pivotable frame structure attached to a said reciprocating element, a pusher element, means pivotably mounting said pusher element on said frame structure, of an air cylinder carried by said frame structure for yieldingly urging said pusher element against said rear end of said sheets in the sheet feeding direction with a variably adjustable pressure, and means for maintaining said pressure substantially constant in said air cylinder in the adjusted condition.

2. The combination according to claim 1, comprising also means operable while the mechanism is running for adjusting said pressure.

3. The combination according to claim 2, in which a separate such pressure adjusting means is provided for each pusher mechanism.

4. The combination according to claim 2, comprising also means for indicating the pressures in said air cylinders.

5. The combination according to claim 1, in which the pressure maintaining means for each air cylinder comprises an adjustable pressure regulation valve and pressure gauges.

6. The combination according to claim 5, in which each said air cylinder comprises a piston having clearance permitting substantially predetermined air leakage at given cylinder pressure and said pressure regulating valve therefor provides a corresponding supply of air. 

